JRA55 tx1 forcing is unphysical (JRA55do is OK)

[phil-blain]

In the process of testing the C grid code with the new areafact computation in a long tx1 simulation, I found out that the current tx1 JRA55 forcing is unphysical, likely coming from the interpolation procedure used to create it.

For example, here are the x-ward winds at the first time slice of year 2005:

Similar patterns can be found for the other years and the rest of the forcing fields. The longitude field in the forcing files is also wrong:

compared to the correct tx1 longitude field (from the tx1 bathymetry file):

Fortunately it seems the newer "JRA55do" data is correctly interpolated.

So this raises a few points:

• What script was used to create the JRA55 data ? to create the JRA5do data ? I found https://github.com/CICE-Consortium/CICE/blob/main/configuration/tools/jra55_datasets/interp_jra55_ncdf_bilinear.py, which dates back from the original addition of JRA55 in e204fb8. But it's unclear if this same script was used to create the JRA55do dataset.
• What should we do with the current JRA55 dataset, which is on Zenodo ? should we create a new version, correctly interpolated, or just deprecate it and use JRA55do for the tx1 grid ?

/cc list based on #435: @daveh150 @rallard77 @dabail10 @apcraig

[dabail10]

Wow. Good catch. I would vote for switching to the JRA55do myself.

[eclare108213]

I thought that we (that would be the "royal we") had done simulations using JRA55 before releasing the code and posting the data. Why didn't they show problems? Has the data been corrupted somehow?

[dabail10]

I think we didn't check the tx1 grid very carefully.

[daveh150]

I made the jra55 and jra55do forcing. They both used the same python xesmf interpolation method.

My local tx1 forcing file (not from zenodo) looks good. I'll download from zenodo and see if that is corrupt somehow.

[phil-blain]

I did re-download from Zenodo yesterday and got the same bad fields, and I checked the md5 checksum was the same as that on Zenodo.

[dabail10]

This is definitely weird. Not sure where in the process this was introduced.

[daveh150]

Thanks Philippe. Yes, strange indeed! Do you have the other years? Is this only int the 2005 file?

[phil-blain]

It's for all the years, all the fields.

[daveh150]

Thank you Phillipe!

Not sure what is happening. A while ago I started running out of local storage space so I removed all the JRA55 files. I can't point for sure if this is somehow in the way I generated the yearly files or something else. Anyway, I will redownload the JRA55 data and regenerate the tx1 forcing for 2005-2009 so we do not have a corrupt set on zenodo.

Sorry for whatever is causing this.

[daveh150]

Best I can tell, when I started to make the tx1 files I moved to another working directory, and I must have accidentally still used the gx1 regridding weight file. (either forgot to change name or type-o).

I have fixed this and reprocessed the data. New dataset is uploading now. It might be done by tomorrow, I'll send the new zenodo link for you to verify.

[apcraig]

The new files should have new names and we need to modify CICE so it picks up the new filenames. Otherwise, there is no way to trap use of the old files and no obvious way to know whether the old or new files are on any given filesystem. This needs to be standard practice when we update a set of files.

[daveh150]

Thanks Tony, it does make sense to keep track of version updates. Does something like ‘JRA55fix’ work? So the new directory/files would be CICE_data/forcing/tx1/JRA55fix/8XDAILY/JRA55fix_03hr_forcing_20050101.nc I think it works with the logic in JRA55_files if the atm_data_type = ‘JRA55fix’. The only code addition could be a check if grid == tx1 and atm_data_type == JRA55 to either abort or change to JRA55fix. I guess the perhaps confusion is the fix is only for tx1 grid, not the other grids. Thanks, Dave

[apcraig]

In general, I sort of wish each forcing filename had a date string in it to indicate when it was created. That also provides easy versioning. But short of that, I don't generally love "fix", my preference would be "v2". But open to hearing other options. We'll need a PR to CICE too.